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Project title: Practical demonstration of scheduling techniques for flowering patio plants


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Project title: Practical demonstration of scheduling techniques for flowering patio plants
Project number: PC 203
Project leader: Dr Steve Adams
Report: Final report, October 2004
Key workers: Warwick HRI:

Dr S. Adams – Project leader

Dr V. Valdes – Project manager

Miss G. Woodward – Project assistant

Mr J. Horridge – Project assistant
HRI Efford:

Dr Ian Clarke – Initiated the project


Location: Warwick HRI, Wellesbourne, Warwick, CV35 9EF
Project co-ordinator: Mr A. Spires - Young Plants Ltd, Church Lane, Alveston, Stratford upon Avon, Warwickshire, CV37 7QJ
Start date: 1 August 2003
Completion date: 31 July 2004
Key words: Flowering, scheduling, temperature, daylength, photoperiod, supplementary lighting, Antirrhinum, Argyranthemum, Bacopa, Bidens, Diascia, Felicia, Fuchsia, Lobelia, Lotus, Nemesia, Petunia, Sanvitalia, Scaevola, Verbena.

Whilst reports issued under the auspices of the HDC are prepared to the best available information, neither the authors nor the HDC can accept any responsibility for inaccuracy or liability for loss, damage or injury from application of any of the concepts or procedures discussed.


The contents of this publication are strictly private to HDC members. No part of this publication may be copied or reproduced in any form or by any means without prior written permission of the Horticultural Development Council.

© 2004 Horticultural Development Council



Contents

Page number


1. Grower Summary 2

1.1. Headline 2

1.2. Background and expected deliverables 2

1.3. Summary of the project and main conclusions 3

1.4. Financial benefits 9

1.5. Action points for growers 10


2. Science section 11

2.1. Introduction 11

2.2. Materials and methods 12

2.3. Results and discussion 14

Antirrhinum LuminaireTM Deep Purple 17

Antirrhinum LuminaireTM Harvest Red 19

Argyranthemum Sultans Dream 21

Bacopa Snowflake 23

Bidens aurea 25

Diascia Joyce’s Choice 27

Felicia Blue 29

Fuchsia Alice Hoffmann 31

Fuchsia Barbara Windsor 33

Fuchsia Betty 35

Fuchsia Dark Eyes 37

Fuchsia Deep Purple 39

Fuchsia Gene 41

Fuchsia Liza 43

Fuchsia Lyle's Unique 45

Fuchsia Marcia 47

Fuchsia Maybe Baby 49

Fuchsia Nice ‘n’ Easy 51

Fuchsia Patio Princess 53

Fuchsia Pink Marshmallow 55

Fuchsia Pink Spangles 57

Lobelia Richardii 59

Lobelia White Star 61

Lotus Bertholetii 63

Nemesia Blue Lagoon 65

Petunia Surfinia Blue 67

Sanvitalia Aztec Gold 69

Scaevola Brilliant 71

Verbena New Ophelia 73

Verbena Red Knight 75

2.4. Conclusions and general discussion 77
3. References 82
Appendix 1 – Experimental plan 83

Appendix 2 – Pictures showing the ‘visible bud’ stages 84



Grower summary

1.1. Headline



  • The project demonstrated how a simple screening protocol could be used to investigate how temperature, daylength and supplementary lighting affect flowering in a range of patio plants.

  • Warmer temperatures hastened flowering in all of the patio plant species/cultivars studied, with the exception of Lotus. Long days promoted flowering in 24 out of the 30 cultivars examined, while supplementary lighting hastened flowering in around half of the cultivars tested.


1.2. Background and expected deliverables
Patio plants have become an increasing part of the bedding and pot plant industry for spring and summer sales. They are often vegetatively propagated and ideally the finished product is sold in flower. Many plants use daylength as a signal for floral induction. However, daylength alone is an ambiguous signal in spring and autumn and, hence, some plants use a combination of photoperiod and chilling to ensure that they flower in spring and not in autumn. Furthermore, temperature usually affects flowering time even in species that do not require chilling. There also is evidence to suggest that for a number of species the time to flowering can be hastened by increased light levels.
This work set out to demonstrate a screening protocol that could be used by growers on their own nurseries to quantify the way in which different species/cultivars respond to their environment, as well as providing valuable information on the responses of 30 different cultivars (14 species). The trial was designed to address the following questions:


  • Does temperature influence the speed of flowering?

  • Do plants develop flowers faster under long/short days?

  • Is flowering improved by the use of supplementary lighting?


1.3. Summary of the project and main conclusions
Patio plants (30 cultivars of 14 different species; Table 1) were obtained as rooted cuttings from commercial propagators. Plants arrived from week 2 to week 5 of 2004. Cuttings were potted up into 9cm pots on arrival at Warwick HRI and placed into a range of different environmental treatments within 4 different glasshouse compartments/blocks.

Experimental Plan




Block 1 Block 2 Block 3 Block 4



SD LD SD LD 5oC 5oC 15oC 15oC


Plants were inspected three times a week so that dates of visible bud appearance and flower opening could be recorded for each plant. The plant height, or in the case of trailing species the length of the longest shoot, was recorded for each plant when 50% of the plants of a given treatment had flowered.


Temperature

Plants were grown in four identical glasshouse compartments each 41m2. Two compartments were set to provide a heating temperature of 5oC, and the other two were set to 15oC. Vent temperatures were set to 3°C above these heating set-points. The 15°C compartments initially ran slightly above this set-point and temperatures were fairly stable, while the 5°C compartment fluctuated more with changes in ambient temperature. The difference between the 5 and 15°C compartments diminished over the course of the experiment as the ambient temperatures increased over time.


Warmer temperatures hastened flowering in 13 out of the 14 species examined (29 out of the 30 cultivars examined) (Table 2). Low temperatures only promoted flowering in Lotus. In nearly all of the cultivars studied warmer temperatures hastened both the appearance of visible buds (Table 1) and the rate of flower development. Therefore, warmer temperatures could be used to hasten flowering of a wide range of patio plants. In most plants this also increased plant growth, although for some may have resulted in a slight loss of compactness. Growth regulators were not used in this trial, and may be used to elevate this problem.
Daylength

At each temperature, one compartment initially provided natural short days (SD), although the daylength increased over the course of the experiment. The other compartment received day-extension lighting (LD) provided by tungsten bulbs (~1.7 µmol/m2/s at bench height (~ 100 lux)) so as to give a minimum daylength of 15 hours (lit from sunset to 23:00 h (GMT)), although this also increased over the course of the experiment due to an earlier sunrise. To avoid problems associated with light pollution in the SD compartments, blackout screens were used on the walls of each compartment from sunset until sunrise.


Most of the species/cultivars were shown to be long day plants (Tables 1 and 2). The only plant in which flowering was hastened by short days was Lotus, while Argyranthemum, Bidens, Diascia, Felicia, and Verbena ‘Red Knight’ showed no significant response to daylength. The response to long day lighting was very pronounced in some species. For example, flowering was hastened by up to 40 days in Petunia (Surfinia). Therefore, there is considerable potential to use day extension or night break lighting to promote flowering, although crops grown slightly later in the year, when daylengths are increasing, may benefit less from this treatment. The fact that very few patio plants are short day plants means that lighting could be used on a combination of species to hasten flowering and make flowering time more predictable. The effect of daylength was often on reducing the time to visible bud; flower development was generally less sensitive to daylength. Therefore, long day lighting would not need to be applied over the whole life of the crop and could be applied for only a limited duration.
A detrimental effect of long day lighting was increased stem elongation (Table 3). If tungsten lamps were used commercially this might result in increased use of growth regulators. However, the increased stem elongation was most likely a result of the red:far-red ratio of the tungsten lamps and not a response to long days per see. Therefore, it would be worth considering the use of other lamp types, for example, compact fluorescent lamps which have a different spectral output.
Light integral (supplementary lighting)

W
Figure 1. Photograph showing the layout of plants and lamps.



ithin each compartment, half of the plants received supplementary lighting, which was provided by two 400W SON/T lamps per compartment. At plant height supplementary light levels were on average 41µmol/m2/s (~3000 lux). SON/T lamps were baffled so that the unlit treatment in the same compartment was unaffected. The supplementary lighting was on for 8 hours per day from 08:00 - 16:00 h (GMT). Natural light levels increased over the course of the experiment and so supplementary lighting gave a proportionally larger effect early in the year when the quantity of natural light was low.
The response to supplementary lighting tended to be less pronounced compared with the effects of temperature and daylength. Supplementary lighting hastened flowering in around half of cultivars studied (Table 2). However, the maximum response was one week. Therefore, the potential for manipulation of flowering through supplementary lighting is limited unless they are used to create long days. The benefits would be greater for early crops. However, the costs of applying supplementary lighting are much greater than the use of low intensity long day lighting using compact fluorescent or tungsten bulbs. Although supplementary lighting may have an added benefit of increasing plant quality as a result of enhanced growth.
Table 1. The effect of temperature, daylength and supplementary lighting on reducing the number of days to visible bud of a range of patio plants. For example, Antirrhinum ‘Deep Purple’ had visible buds 28 day sooner in the 15°C set-point compartments when compared with the 5°C compartments.

Cultivar

Reduction in the time to visible bud (days)

Temperature

Daylength

Light integral

5°C

15°C

SD

LD

-SON/T

+SON/T

Antirrhinum Lum. Deep Purple




28




131




5

Antirrhinum Lum. Harvest Red




22




10







Argyranthemum Sultans Dream




9










5

Bacopa Snowflake



















Bidens aurea




7













Diascia Joyce’s Choice




25










7

Felicia Blue
















4

Fuchsia Alice Hoffmann




373




171







Fuchsia Barbara Windsor




253




201




3

Fuchsia Betty




13




101,5




3

Fuchsia Dark Eyes




32




301,5







Fuchsia Deep Purple




29




245







Fuchsia Gene




25




12




3

Fuchsia Liza




27




245







Fuchsia Lyle's Unique




155




195




3

Fuchsia Marcia




22




5







Fuchsia Maybe Baby




13




131,5







Fuchsia Nice ‘n’ Easy




283




121




5

Fuchsia Patio Princess




21




15




46

Fuchsia Pink Marshmallow




243




211







Fuchsia Pink Spangles




293




201




2

Lobelia Richardii




93




271







Lobelia White Star




16




22







Lotus Bertholetii

See text




See text







See text

Nemesia Blue Lagoon




9










6

Petunia Surfinia Blue




273




461







Sanvitalia Aztec Gold




354




142







Scaevola Brilliant




19




>10




7

Verbena New Ophelia




19




10




3

Verbena Red Knight




8










8


1 Difference reduced if temperature reduced 4 Difference reduced if LD

2 Difference reduced if temperature increased 5 Difference reduced if pinched

3 Difference reduced if SD 6 Difference reduced if in larger plug

Table 2. The effect of temperature, daylength and supplementary lighting on reducing the number of days to flower opening of a range of patio plants. For example, Antirrhinum ‘Deep Purple’ had open flowers 30 day sooner in the 15°C set-point compartments when compared with the 5°C compartments.

Cultivar

Reduction in the time to open flowers (days)

Temperature

Daylength

Light integral

5°C

15°C

SD

LD

-SON/T

+SON/T

Antirrhinum Lum. Deep Purple




30




131




4

Antirrhinum Lum. Harvest Red




27




8







Argyranthemum Sultans Dream




16













Bacopa Snowflake




27




4




4

Bidens aurea




18













Diascia Joyce’s Choice




28










6

Felicia Blue




10










5

Fuchsia Alice Hoffmann




383




161







Fuchsia Barbara Windsor




293




211




4

Fuchsia Betty




20




111,5







Fuchsia Dark Eyes




37




291,5







Fuchsia Deep Purple




30




185







Fuchsia Gene




31




11




4

Fuchsia Liza




33




255




3

Fuchsia Lyle's Unique




205




155




3

Fuchsia Marcia




29













Fuchsia Maybe Baby




225




121,5







Fuchsia Nice ‘n’ Easy




333




121




5

Fuchsia Patio Princess




306




121







Fuchsia Pink Marshmallow




23




211







Fuchsia Pink Spangles




313




211




2

Lobelia Richardii




273




281







Lobelia White Star




263




201




2

Lotus Bertholetii

See text




See text







See text

Nemesia Blue Lagoon




22




2




6

Petunia Surfinia Blue




363




401







Sanvitalia Aztec Gold




384




122




3

Scaevola Brilliant




443




141




5

Verbena New Ophelia




28




13







Verbena Red Knight




8










7


1 Difference reduced if temperature reduced 4 Difference reduced if LD

2 Difference reduced if temperature increased 3 Difference reduced if SD

5 Difference reduced if pinched 6 Difference reduced if in larger plug
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